The long-term objective of this study is to contribute to the better understanding of the mechanisms involved in mammalian fertilization. In this study, the major emphasis will be placed on the biology and physiology of mammalian sperm nucleus. Syrian hamsters, mice and rabbits will be used as model animals. Specific questions we intend to answer are: 1) Is the nucleus the only sperm component contributing to the zygote development? 2) If the zygote requires more than the sperm nucleus for its development, what is/are the sperm's component(s) contributing to it? 3) Will it be possible to distinguish genetically abnormal sperm nuclei from normal ones prior to incorporation (injection) into oocytes? 4) Will it be possible to store isolated sperm nuclei without destroying their genetic integrity? 5) When does the sperm nucleus become genetically functional? Seeking answers to such fundamental and teleological questions is not only of academic curiosity, but also may contribute to the advancement of medical and agricultural technology.